For the Italy data and Belgium data of Table, what is the ratio of the difference between the average variance minus average covariance and the average covariance? If the average variance of a single security is 50, what is the expected variance of a portfolio of 5, 20, and 100 securities?
United States ......... 73
United Kingdom ....... 65.5
France ............. 67.3
Germany ......... 56.2
Italy ............ 60.0
Belgium ......... 80.0
Switzerland ......... 56.0
Netherlands ......... 76.1
International stocks ..... 89.3